Provided by: grass-doc_7.6.0-1_all
v.kcv - Randomly partition points into test/train sets.
vector, statistics, points, point pattern
v.kcv v.kcv --help v.kcv map=name [layer=string] npartitions=integer [column=name] [--help] [--verbose] [--quiet] [--ui] Flags: --help Print usage summary --verbose Verbose module output --quiet Quiet module output --ui Force launching GUI dialog Parameters: map=name [required] Name of vector map Or data source for direct OGR access layer=string Layer number or name Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name. Default: 1 npartitions=integer [required] Number of partitions Must be > 1 column=name Name for new column to which partition number is written Default: part
v.kcv randomly divides a points lists into k sets of test/train data (for npartitions-fold cross validation). Test partitions are mutually exclusive. That is, a point will appear in only one test partition and k-1 training partitions. The module generates a random point using the selected random number generator and then finds the closest point to it. This site is removed from the candidate list (meaning that it will not be selected for any other test set) and saved in the first test partition file. This is repeated until enough points have been selected for the test partition. The number of points chosen for test partitions depends upon the number of sites available and the number of partitions chosen (this number is made as consistent as possible while ensuring that all sites will be chosen for testing). This process of filling up a test partition is done k times.
An ideal random sites generator will follow a Poisson distribution and will only be as random as the original sites. This module simply divides vector points up in a random manner. Be warned that random number generation occurs over the intervals defined by the current region of the map. This program may not work properly with Lat-long data.
All examples are based on the North Carolina sample dataset. g.copy vect=geonames_wake,my_geonames_wake v.kcv map=my_geonames_wake column=part npartitions=10 g.copy vect=geodetic_pts,my_geodetic_pts v.kcv map=my_geodetic_pts column=part npartitions=10
James Darrell McCauley, when he was at: Agricultural Engineering Purdue University 27 Jan 1994: fixed RAND_MAX for Solaris 2.3 13 Sep 2000: released under GPL Updated to 5.7 Radim Blazek 10 / 2004 OGR support by Martin Landa (2009) Speed-up by Jan Vandrol and Jan Ruzicka (2013) Last changed: $Date: 2014-11-28 17:22:17 +0100 (Fri, 28 Nov 2014) $
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